1. Field of the Invention
The present invention relates to the field of apex fittings clevises and the like.
2. Prior Art
Metal clevises of various designs and structures are well-known in the prior art. Such devices are generally characterized by an approximately U-shaped main body with an eye in the end of each leg of the U, the eyes being generally axially aligned to receive a pin therethrough. Frequently, one of the eyes and one end of the pin are both threaded so that the pin may be threaded into place and locked into position with respect to the clevis. Such devices are widely used, finding broad application from very small sizes to very large sizes.
In many applications, metal clevises are ideal as being relatively inexpensive, sufficiently strong and easy to use. In certain applications, however, metal clevises and clevis-like structures, because of the loads involved, are heavy and inconvenient to use. Shear weight alone may make the clevises difficult to manipulate, aggravated by the fact that the clevis and clevis-pin must be separately manipulated. Further, the weight itself creates a safety hazard, as a reasonable impact between, say, a forty-pound clevis and an equal or larger crane hook can have a bone-crushing effect on a finger inadvertently located therebetween.
One typical application for clevis-like structures is apex fittings. Such fittings, which frequently are metal clevis-like structures, receive the lifting straps on cargo nets and are intended for hooking over a crane hook to provide the central lifting point. Such devices are used on ordinary cranes, shipboard cranes and even helicopter cranes wherein the loads being lifted at any one time may run many tens of thousands of pounds. Frequently the load to be lifted prevents or inhibits convenient disposal of the apex fitting so that the user winds up reaching out at arm's length to lift the clevis and manipulate the clevis pin. Accordingly, lighter and/or more convenient devices are highly desirable and have been the subject of substantial effort by others.
In U.S. Pat. No. 3,079,192, a cargo sling is disclosed which is formed or wire rope or the like. The sling is characterized by a rope-like assembly having a loop at each end protected by a sheath. The sling is fabricated by spacing the sheaths as desired and then hooking one end of the rope over one sheath, winding it down around the second sheath, up over the start end of the rope on the first sheath and down again, with the finished end of the rope being tucked between the loop formed by the winding and the second sheath. With this construction, the load on the main loops increases the frictional engagement of the rope ends to help avoid slippage thereof. The resulting rope-like assembly is therefore comprised of three lengths of the rope or cable. In U.S. Pat. No. 2,199,958, a hoisting sling of generally similar construction is shown with one embodiment being formed of a single length of cable so that the body consists of three cables and the eyes consist of two cables, and the second embodiment being formed of two cables to provide a body formed of four cables and eyes consisting of three cables. U.S. Pat. No. 3,222,858 discloses a twisted cable assembly and method of making the assembly which utilizes a single strand of wire looped over a pair of spaced apart pins a substantial number of times, and then twisted about its length to form a central section of twisted wire cable with continuous loops of wire at each end thereof. In an alternate method of making the twisted cable assembly the wire is pre-twisted along its axis so that after winding around the spaced-apart pins the untwisting of the individual wires will form the twist of the desired finished cable.
In addition to the foregoing patents, U.S. Pat. No. 3,631,733 discloses an elastic transmission belt of single loop twisted construction, with the looped ends thereof being held together by a metal clip. Also, U.S. Pat. No. 4,045,072 discloses an abrasion-resistant boot and pendant or sling of wrapped construction.